Dagger2 缺少绑定无法提供 ViewModel 密钥

Question

我正在尝试使用具有多重绑定的 Dagger2 创建我的 ViewModel 的依赖注入，但我收到此错误并且我无法使其工作，我尝试了几个答案（如下）但是 none他们中的一些人帮助了我。

这是我收到的错误：

SaveMyHeroApplicationComponent.java:8: error: [Dagger/MissingBinding] java.util.Map<java.lang.Class<? extends androidx.lifecycle.ViewModel>,javax.inject.Provider<androidx.lifecycle.ViewModel>> cannot be provided without an @Provides-annotated method.

这是我的代码

class SaveMyHeroApplication : DaggerApplication() {

    override fun applicationInjector(): AndroidInjector<out DaggerApplication> {
        return DaggerSaveMyHeroApplicationComponent.factory().create(this)
    }
}

@Singleton
@Component(modules = [AndroidInjectionModule::class, MainActivityModule::class])
interface SaveMyHeroApplicationComponent : AndroidInjector<SaveMyHeroApplication> {

    @Component.Factory
    interface Factory {
        fun create(@BindsInstance context: Context): SaveMyHeroApplicationComponent
    }
}

@Module(includes = [NetworkModule::class, HomeModule::class])
class MainActivityModule {

    @Provides
    fun provideViewModelFactoryProviders(
        providers: Map<Class<out ViewModel>, @JvmSuppressWildcards Provider<ViewModel>>
    ): ViewModelProvider.Factory = SaveMyHeroViewModelFactory(providers)
}

class SaveMyHeroViewModelFactory(
    private val providers: Map<Class<out ViewModel>, Provider<ViewModel>>
) : ViewModelProvider.Factory {

    override fun <T : ViewModel> create(modelClass: Class<T>): T =
        requireNotNull(getProvider(modelClass).get()) {
            "Provider for $modelClass returned null"
        }


    private fun <T : ViewModel> getProvider(modelClass: Class<T>): Provider<T> =
        try {
            requireNotNull(providers[modelClass] as Provider<T>) {
                "No ViewModel provider is bound for class $modelClass"
            }
        } catch (error: ClassCastException) {
            error("Wrong provider type registered for ViewModel type $error")
        }
}


@Module(includes = [HomeModule.ProvideViewModel::class])
abstract class HomeModule {

    @ContributesAndroidInjector(modules = [InjectViewModel::class])
    abstract fun bind(): HomeFragment

    @Module
    class ProvideViewModel {

        @Provides
        @IntoMap
        @ViewModelKey(HomeViewModel::class)
        fun provideHomeViewModel() = HomeViewModel()
    }

    @Module
    class InjectViewModel {

        @Provides
        fun provideHomeViewModel(
            factory: ViewModelProvider.Factory,
            target: HomeFragment
        ) = ViewModelProvider(target, factory).get(HomeViewModel::class.java)
    }
}

@MustBeDocumented
@Target(
    AnnotationTarget.FUNCTION,
    AnnotationTarget.PROPERTY_GETTER,
    AnnotationTarget.PROPERTY_SETTER
)
@Retention(AnnotationRetention.RUNTIME)
@MapKey
annotation class ViewModelKey(val value: KClass<out ViewModel>)

此外，这些是我的应用依赖版本：

 kotlin_version = ‘1.3.72'
 dagger_version = ‘2.27’

 gradle:3.6.3

我知道这个问题有几个问题，但我尝试了几个，none 其中对我有用。

这是我尝试阅读和检查的解决方案链接：

https://github.com/android/architecture-components-samples/tree/master/GithubBrowserSample

https://github.com/google/dagger/issues/1478

https://medium.com/chili-labs/android-viewmodel-injection-with-dagger-f0061d3402ff

https://github.com/ChiliLabs/viewmodel-dagger-example

Answer 1

尝试以Architecture Blueprints sample (dagger-android branch)为例。

Dagger Android 本身就是一团糟，重要的是要遵循一些模板不要走错路。可能您的方法也可以修复，但我建议您尝试更改架构：

您的自定义视图模型工厂应该在构造函数中包含@Inject：

class SaveMyHeroViewModelFactory @Inject constructor(
    private val creators:  @JvmSuppressWildcards Map<Class<out ViewModel>, Provider<ViewModel>>
) : ViewModelProvider.Factory {
.......

您应该添加辅助模块 ViewModelBuilderModule，它提供 ViewModelProvider.Factory（您在所有活动和片段中注入）和您的自定义 ViewModel.Factory:

@Module
abstract class ViewModelBuilderModule {
    @Binds
    abstract fun bindViewModelFactory(factory: SaveMyHeroViewModelFactory): ViewModelProvider.Factory
}

对于你的所有对 - Activitiy/ViewModel 和 Fragment/ViewModel 你应该像这样添加模块（但你可以为所有的人制作一个模块，这取决于你）：

@Module
abstract class HomeModule {

    @ContributesAndroidInjector(modules = [ViewModelBuilderModule::class])
    internal abstract fun bind(): HomeFragment

    @Binds
    @IntoMap
    @ViewModelKey(HomeViewModel::class)
    internal abstract fun provideHomeViewModel(viewModel: HomeViewModel): ViewModel
}

在您的 Dagger 组件中，您应该使用第 3 步中的所有模块：

@Singleton
@Component(modules = [AndroidSupportInjectionModule::class, HomeModule::class, ...])
interface SaveMyHeroApplicationComponent : AndroidInjector<SaveMyHeroApplication> {

    @Component.Factory
    interface Factory {
        fun create(@BindsInstance context: Context): SaveMyHeroApplicationComponent
    }
}

Dagger2 缺少绑定无法提供 ViewModel 密钥

Dagger2 Missing Binding Cannot Provides ViewModel Key

android

dependency-injection

kotlin

dagger-2

android-viewmodel